Electrical installation trunking is commonly used, for example in domestic, industrial, academic, military, government, office and public environments for holding and positioning cables and wires. The trunking, which is commonly formed as a U-shaped channel, is fastened to the building infrastructure. Cables are inserted into the trunking and are sometimes retained by clips, before a cover is attached to the U-shaped channel.
Without clips, the cabling has a tendency to sag under its own weight out of the trunking, making it difficult for the installer to fit the cover. When fitting the trunking to a ceiling, for example, the cables tend to drop out of the trunking and clips are required to retain the cabling. This problem occurs whether trunking and cabling are being fitted during an initial installation, or at a later date when additional cabling is being added into existing trunking. Clips are located at intervals along the length of the trunking to provide support to the cabling before the cover is finally attached.
In industrial applications, metal trunking is used. For example, in the construction of new buildings, metal trunking or conduit is often sunk into masonry and attached thereto by screws. In other applications such as lighting and retrofit cable distribution, the trunking may be suspended from the building infrastructure. This typically means that cable insertion is carried out above ground and sometimes at arm's reach. Fitting clips that require use of a tool can be awkward and generally slows down the pace of an installation, especially if the installer is trying to fit a clip with one hand whilst holding the cabling within the trunking with his other hand.
By contrast, PVC trunking tends to be used more for holding and positioning cables where the aesthetics of the trunking are important, for example on walls and ceilings, and adjacent to skirting boards. PVC trunking is usually surface mounted and due to its lightness can be fastened with self-adhesive strips. PVC trunking covers are commonly attached to the U-shaped channel with a snap-fit assembly. Each U-shaped channel has a base and a pair of sidewalls each terminating in an inwardly facing flange. In a PVC snap-fit assembly, the inwardly facing flange may be angled or perpendicular to the side walls and the edges of the cover engage the flanges with a snap-fit.
Snap-fit arrangements can be found in metal trunking but metal trunking covers are more often attached to the base using a screw arrangement, such as a turnbuckle, or some other mechanical means. To lock the cover in place on the base, a screwdriver is used to turn the turnbuckle until the turnbuckle rotates into position underneath the flange. A problem with this type of arrangement is that when the trunking is full of cables or wires, the turnbuckle can damage any cables or wires proximate the flange, especially because the turnbuckle may be made from metal. This can potentially lead to short-circuits within the trunking when the cables are eventually in operation.
Currently, available clips generally used in plastic trunking, take the form of resilient C-shaped members, which are inserted whilst in a compressed state into the trunking and which then flex back into their natural position, wedging under the flanges of the trunking. In this way, the cables are retained within the trunking. A disadvantage of the C-shape is that it significantly reduces the available capacity within trunking for the cabling. Also, each clip is suitable for use with only one width of trunking. This means that for any particular job, the installer must transport quantities of each size of clip in case they are required for fitment with a range of sizes of trunking.
It is an object of the invention to provide an adjustable clip which reduces or substantially obviates the above mentioned problems.